Implement new panic!() behaviour for Rust 2021.

Author: m-ou-se

core/src/macros/mod.rs

@@ -1,3 +1,4 @@
+#[cfg(bootstrap)]
 #[doc(include = "panic.md")]
 #[macro_export]
 #[allow_internal_unstable(core_panic)]
@@ -18,6 +19,21 @@ macro_rules! panic {
     );
 }
 
+#[cfg(not(bootstrap))]
+#[doc(include = "panic.md")]
+#[macro_export]
+#[rustc_builtin_macro = "core_panic"]
+#[allow_internal_unstable(edition_panic)]
+#[stable(feature = "core", since = "1.6.0")]
+#[rustc_diagnostic_item = "core_panic_macro"]
+macro_rules! panic {
+    // Expands to either `$crate::panic::panic_2015` or `$crate::panic::panic_2021`
+    // depending on the edition of the caller.
+    ($($arg:tt)*) => {
+        /* compiler built-in */
+    };
+}
+
 /// Asserts that two expressions are equal to each other (using [`PartialEq`]).
 ///
 /// On panic, this macro will print the values of the expressions with their

core/src/panic.rs

@@ -5,6 +5,40 @@
 use crate::any::Any;
 use crate::fmt;
 
+#[doc(hidden)]
+#[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
+#[allow_internal_unstable(core_panic)]
+#[rustc_diagnostic_item = "core_panic_2015_macro"]
+#[rustc_macro_transparency = "semitransparent"]
+pub macro panic_2015 {
+    () => (
+        $crate::panicking::panic("explicit panic")
+    ),
+    ($msg:literal $(,)?) => (
+        $crate::panicking::panic($msg)
+    ),
+    ($msg:expr $(,)?) => (
+        $crate::panicking::panic_str($msg)
+    ),
+    ($fmt:expr, $($arg:tt)+) => (
+        $crate::panicking::panic_fmt($crate::format_args!($fmt, $($arg)+))
+    ),
+}
+
+#[doc(hidden)]
+#[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
+#[allow_internal_unstable(core_panic)]
+#[rustc_diagnostic_item = "core_panic_2021_macro"]
+#[rustc_macro_transparency = "semitransparent"]
+pub macro panic_2021 {
+    () => (
+        $crate::panicking::panic("explicit panic")
+    ),
+    ($($t:tt)+) => (
+        $crate::panicking::panic_fmt($crate::format_args!($($t)+))
+    ),
+}
+
 /// A struct providing information about a panic.
 ///
 /// `PanicInfo` structure is passed to a panic hook set by the [`set_hook`]

std/src/lib.rs

@@ -258,6 +258,7 @@
 #![feature(dropck_eyepatch)]
 #![feature(duration_constants)]
 #![feature(duration_zero)]
+#![feature(edition_panic)]
 #![feature(exact_size_is_empty)]
 #![feature(exhaustive_patterns)]
 #![feature(extend_one)]

std/src/macros.rs

@@ -4,6 +4,7 @@
 //! library. Each macro is available for use when linking against the standard
 //! library.
 
+#[cfg(bootstrap)]
 #[doc(include = "../../core/src/macros/panic.md")]
 #[macro_export]
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -17,6 +18,21 @@ macro_rules! panic {
     });
 }
 
+#[cfg(not(bootstrap))]
+#[doc(include = "../../core/src/macros/panic.md")]
+#[macro_export]
+#[rustc_builtin_macro = "std_panic"]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[allow_internal_unstable(edition_panic)]
+#[cfg_attr(not(test), rustc_diagnostic_item = "std_panic_macro")]
+macro_rules! panic {
+    // Expands to either `$crate::panic::panic_2015` or `$crate::panic::panic_2021`
+    // depending on the edition of the caller.
+    ($($arg:tt)*) => {
+        /* compiler built-in */
+    };
+}
+
 /// Prints to the standard output.
 ///
 /// Equivalent to the [`println!`] macro except that a newline is not printed at

std/src/panic.rs

@@ -17,6 +17,36 @@ use crate::sync::{Arc, Mutex, RwLock};
 use crate::task::{Context, Poll};
 use crate::thread::Result;
 
+#[doc(hidden)]
+#[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
+#[allow_internal_unstable(libstd_sys_internals)]
+#[cfg_attr(not(test), rustc_diagnostic_item = "std_panic_2015_macro")]
+#[rustc_macro_transparency = "semitransparent"]
+pub macro panic_2015 {
+    () => ({
+        $crate::rt::begin_panic("explicit panic")
+    }),
+    ($msg:expr $(,)?) => ({
+        $crate::rt::begin_panic($msg)
+    }),
+    ($fmt:expr, $($arg:tt)+) => ({
+        $crate::rt::begin_panic_fmt(&$crate::format_args!($fmt, $($arg)+))
+    }),
+}
+
+#[doc(hidden)]
+#[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
+#[allow_internal_unstable(libstd_sys_internals)]
+#[rustc_macro_transparency = "semitransparent"]
+pub macro panic_2021 {
+    () => ({
+        $crate::rt::begin_panic("explicit panic")
+    }),
+    ($($t:tt)+) => ({
+        $crate::rt::begin_panic_fmt(&$crate::format_args!($($t)+))
+    }),
+}
+
 #[stable(feature = "panic_hooks", since = "1.10.0")]
 pub use crate::panicking::{set_hook, take_hook};